For patients with a high degree of spinal instability (e.g. fractures), or in revision surgery, a combination anterior/posterior fusion is indicated at one or more levels. Fusing both the front and back provides a high degree of stability for the spine and a large surface area for the bone fusion to occur. The disc may be approached either as an anterior lumbar interbody fusion (ALIF), or as a posterior lumbar interbody fusion (PLIF). Transforaminal lumbar interbody fusion (TLIF) fuses the anterior and posterior columns of the spine through a single posterior approach. All such procedures are well known to those of skill in the art.
To further stabilize vertebral segments, posterior instrumentation is often performed in conjunction with an interbody fusion. The most commonly used posterior instrumentation system in use today is pedicle screw fixation. The major disadvantage to this technique is the necessity of major muscle dissection, which can lead to morbidity and scarring. Another disadvantage is the bulkiness of the pedicle/rod system, which has the potential of being prominent, palpable, or painful.
Facet screw fixation offers the advantage of placing a single screw across each articulating facet joint to immobilize a motion segment, thereby reducing the amount of hardware (and therefore exposure) necessary. Existing techniques, however, still demand relatively open procedures, such that the need remains for a facet fixation system compatible with minimally invasive surgical (MIS) procedures.